Cutting tool



Patented Nov. 16, 1943 CUTTING TOOL Charles Burgess and William D. Forgeng, Niagara Falls, N. Y., assignors to Haynes Stellite Company, a corporation of Indiana No-Drawing. Original application July 30, 1940, Serial No. 348,445, now Patent No. 2,297,687, dated October 6, 1942. Divided and this application November 15, 1941, Serial No. 419,289

2 Claims.

' This invention relate to abrasion resistant a1 loys of the type composed principally of chromium and iron, and to new and useful cutting tools made therefrom. This application is a. division of our copending application, Serial No. 348,445, filed July 30, 1940, which has matured into Patent No. 2,297,687, of October 6, 1942.

Chromium-iron'alloy's, often modified by the addition of other elements, have been used to resist wear and abrasion. By varying the composition, and in some instances the heat treatment, ithas been possible to vary the hardness, tough-- ness, and strength of the alloys over wide ranges. But hardness of a very high degree such as is 'required 'of a metal-cutting tool has heretofore been accompanied by an undue degree'of brittleness. Cutting tool high speed steels have been basically tungsten-iron compositions rather than chromium-iron, and have typically contained 18% tungsten, 4% chromium, and 1% vanadium (so-called 18-4-1) sometimes modified by the addition of one or more of the metals cobalt,

nickel, and molybdenum.

It is a primary object of the invention to provide an abrasion resistant chromium iron alloy which, in the form of a cutting tool, will cut metals at high speeds at least as well as 18-4-1 high speed steel.

We have discovered that a hard chromium-' after described,

More specifically, according to the invention,-

chromium alloy and cutting tools comprise compositions substantially within the following percentage limits:

Broad Preferred Per cent chromium 45 to 65 50 to 56 Per cent cobalt 5 to 20 7 to 15 Per cent nickeL. 4 to.20 6 to 15 Per cent silicon. 0. 05 to 5 0.2 to 2 Per cent boron. -0. 05 to 5 0.2 to 1.5 Per cent carbon 1 I to 3 1.5 to 2. 25

sirable to add manganese up to about 10%. The normal impurities of steels, such as phosphorus, sulfur, and nitrogen, may be present in small fractional percentages without departing from the invention.

The alloy tools of this invention may be used in the as-cast condition (after casting in sand or carbon molds forinstance) or when heat treated. A suitable heat treatment consists in holding the alloy tools at a temperature between about 550 C. and about 850 C. for a time-between about five minutes at the higher temperatures to about twenty hours at the lower temperatures. The alloys are hot forgeable to a limited extent. If the alloys are to be forged, it is best to begin that operation before they have cooled' from the casting step to below 900 C. Some cold deformation of the forged alloy can be effected, preferably after quenching from above 900 C.

Depending chiefly upon the composition and heat treatment, the hardness of the alloy of the invention varies between the approximate limits of 55 to '70 Rockwell C. The best cutting tool quality is usually attained in tools having a hardness in the, neighborhood of 60 Rockwell C.

. The transverse strength of the as-cast alloy is upwards of 1000 pounds (loading applied centrally to a section 0.5 inch by 0.5 inch square, supported in a 4 inch span) and in the preferred range of compositions attains 3000 to 4000 pounds and sometimes more.

Cutting tests indicate that the alloy tool ofthe invention compares favorably with standard high speed steel tools of the 18-4-1 type. In accelerated life tests, cutting steel billets and semisteel billets, and using surface speeds, feeds, and cuts considerably greater than normal, tools of this invention cut from two to eight times as far as standard Rex AAA, a widely used high speed steel of high quality.

Although the use of the alloy of this invention as a cutting tool has been emphasized in the fore- I "machinery wear-resisting parts.

The iron being usually more than 15% and pref eralols, at least 20%. On occasion it will be de- We claim: 3

1. A heat-treated high speed, metal-cutting tool having substantially the composition: between 45% and chromium, between 5% and 20% cobalt, between 4% and 20% nickel, between 0.05% and 5% silicon, between 0.05% and 5% boron, between 1.5% and 3% carbon, remainder iron; and being in the condition resulting from being heated at a temperature within the range 5 50912. to 850 C. for a time between five minutes iron content being more than 15%; and being in the condition resulting from being heated at I a temperature within-the range 550 C. to 850 C. for a time between five minutes and twenty 'CHARLES o. BURGESS.

WILLIAM n. FORGENG.

5 hours. 

